A wide variety of manual knife sharpeners have been used for centuries but most of these have been disappointing because they did not provide any precise means to control the sharpening angle. The importance of angle control to the creation of ultra sharp knife edges is recognized in, for example, U.S. Pat. Nos. 5,390,431 and 4,627,194.
Manual sharpeners have been described by others where control of the sharpening angle is obtained by use of clamping devices or blade carriers in which the blade is mounted in a mechanism and physically restrained so that the facet of the blade edge is restrained to remain parallel to the abrasive sharpening surface as the clamping device or carrier is moved in a predetermined direction relative to the abrasive sharpening surface. A major disadvantage of using clamping devices or carriers to control sharpening angle is the awkwardness and inconvenience of the devices themselves.
One example of such blade carriers, U.S. Pat. No. 2,652,667 by C. D. Arnold, describes a sharpener where the blade is placed in a knife blade holder which moves in a direction parallel to the surface of the sharpening stone while the blade facet is in contact with the abrasive stone. The blade is wedged into the blade holder that sets the blade at a predetermined angle to the abrasive surface. Another example is U.S. Pat. No. 3,882,642 by C. S. Sykes, which describes a different knife holder that moves in a direction parallel to the surface of the sharpening stone. The blade is held in fixed non-sliding contact with the holder as the holder is moved in a direction parallel to the abrasive surface. AS the holder moves the knife edge moves with it in contact with the abrasive surface.
This application relates to techniques to incorporate convenient yet precise angle control to a variety of manual knife sharpeners.
Advantages of manual sharpeners as a class are their simplicity, portability, and ease of use. The new and novel guide structure described here preserves these advantages while permitting control of the blade to be totally manual and where its control is entirely free of any clamping device or carrier, yet one is able to maintain a consistent sharpening angle stroke-after-stroke. This new concept can be implemented in a wide variety of physical configurations while incorporating any of the well-known abrasive surfaces.
This novel structure of angle control provides a displaceable physical linear guide surface against which the face of the blade is manually positioned and manually aligned in sliding contact with that surface as the facet of that blade is manually caused to traverse along an abrasive surface. The axis of the displaceable linear surface is restrained to move only in a direction perpendicular to its linear guide surface so that the axis of the displaced linear guide surface, however, displaced will always remain parallel to its previous alignment. By manually maintaining the face of the blade in full sliding contact and in alignment with the linear guide surface as the facet of the blade edge is moved across or along the abrasive surface, excellent control of the sharpening angle is insured and an extremely sharp edge is created. The grit size and the type of abrasive can be selected to be more or less aggressive depending on the dullness of the edge. By changing the angle between the linear guide surface and the plane of the abrasive surface the sharpening angle of the blade can be varied to suit the users need. Sharpening of a blade can be conducted in one or more stages of progressively larger sharpening angle and finer grits so as to establish one or more edge facet angles and improve the perfection of the ultimate edge.
The linear guide surface can be located in front of the abrasive, as seen by the user, behind the abrasive, or in the middle of the abrasive plane. In the last case the abrasive would be located in front of and behind the linear guide surface.